The sense of taste is fundamental in determining nutrient and food selection and therefore the health of the organism. The long-term goal of this laboratory is to elucidate the biochemical and molecular mechanisms of taste transduction. Recent biochemical evidence in the channel catfish (Ictalurus punctatus) suggests a role in taste perception for the unconventional signalling molecule nitric oxide. The specific aim of the project is to clone the gene(s) encoding the enzyme(s) - nitric oxide synthase, or NOS - responsible for the biosynthesis of nitric oxide in the taste organ of the catfish. To achieve this aim the method known as homology cloning will be employed. Using DNA from the catfish taste organ as the template, together with primer pairs complementary in sequence to previously cloned isoforms of NOS, PCR experiments will be performed to amplify gene fragments encoding NOS-related proteins. Using the fragments so obtained as molecular probes, representative cDNA libraries prepared from the catfish taste organ will he screened to locate the full- length clone(s) encoding the NOS gene(s). These will then be characterized in terms of their primary nucleotide sequence, deduced amino acid sequence, tissue distribution and relationship to known members of the NOS family of genes.